It's not bad at all, I really enjoy it. The device performs wonderfully, as all GS3's do. And, the service is great, except for the fact that Metro's 4G is about as fast as 3G.
I have no issue with it thus far, but I've only had it for a few days.

I love using metro in combo with my s3. At first I was getting 7-8mbps down but now am fairly consistently getting 5.5-7mbps down, which is still perfectly acceptable IMO. I love having unthrottled unlimited data like this without the hefty price

MetroPCS has improved so much over the past couple of years. I checked my local coverage with them and took a chance coming from AT&T. I actually can't remember the last time I had a dropped call. If you're in the right area, service in general is extremely reliable.